U.S. patent number 5,782,730 [Application Number 08/686,055] was granted by the patent office on 1998-07-21 for pressure roller.
This patent grant is currently assigned to Arai Seisakusho Co., Ltd.. Invention is credited to Hiroshi Kawasaki, Shigeru Maruyama.
United States Patent |
5,782,730 |
Kawasaki , et al. |
July 21, 1998 |
Pressure roller
Abstract
A pressure roller is disclosed which comprises: a metal core; an
elastic layer formed around the metal core; and a top layer
provided over the elastic layer, the top layer having a thickness
of not greater than 0.1 mm and being made of a fluororesin, the
fluororesin having a coefficient of dynamic friction of 0.25 or
more. The pressure roller is capable of forming a high quality
image free of image failure and has excellent durability. The
fluororesin having a coefficient of dynamic friction as high as
0.25 or more can be obtained by incorporation of a second component
having high viscoelasticity into a fluororesin such as PFA, FEP,
MFA or EPA.
Inventors: |
Kawasaki; Hiroshi (Tokyo,
JP), Maruyama; Shigeru (Tokyo, JP) |
Assignee: |
Arai Seisakusho Co., Ltd.
(Tokyo, JP)
|
Family
ID: |
16309843 |
Appl.
No.: |
08/686,055 |
Filed: |
July 24, 1996 |
Foreign Application Priority Data
|
|
|
|
|
Jul 23, 1996 [JP] |
|
|
8-193544 |
|
Current U.S.
Class: |
492/56;
492/59 |
Current CPC
Class: |
G03G
15/206 (20130101) |
Current International
Class: |
G03G
15/20 (20060101); B23P 015/00 () |
Field of
Search: |
;492/56,59
;428/35.7,36.5 ;399/279 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Cuda; Irene
Claims
What is claimed is:
1. A pressure roller comprising:
a metal core,
an elastic layer formed around said metal core, and
a top layer provided over said elastic layer, said top layer having
a thickness of not greater than 0.1 mm and being made of a
fluororesin, said fluororesin having a coefficient of dynamic
friction of 0.25 or more.
2. The pressure roller according to claim 1, wherein said elastic
layer is made of a silicone rubber or a silicone sponge rubber.
3. The pressure roller according to claim 1 or 2, wherein said
fluororesin is mixed with at least one member selected from the
group consisting of a polyamide, a polyester, a thermoplastic
fluororubber, a tetrafluoroethylene-hexafluoropropylene copolymer
(ETFE), and a tetrafluoroethylene-hexafluoropropylene-vinylidene
fluoride terpolymer (THV).
4. The pressure roller according to claim 1, wherein the
fluororesin is made of a tetrafluoroethylene-perfluoroalkyl vinyl
ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene
copolymer (FEP), tetrafluoroethylene-perfluoromethyl vinyl ether
copolymer (MFA) or
tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether
terpolymer (EPA).
5. A pressure roller comprising:
a metal core,
an elastic layer formed around said metal core, and
a top layer provided over said elastic layer, said top layer having
a thickness of not greater than 0.1 mm and being made of a
fluororesin, wherein the fluororesin is a
tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA),
tetrafluoroethylene-hexafluoropropylene copolymer (FEP),
tetrafluoroethylene-perfluoromethyl vinyl ether copolymer (MFA) or
tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether
terpolymer (EPA), and is mixed with at least one member selected
from the group consisting of a polyamide, a polyester, a
thermoplastic fluororubber, a
tetrafluoroethylene-hexafluoropropylene copolymer (ETFE), and a
tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride
terpolymer (THV).
6. The pressure roller of claim 5 wherein said elastic layer is
made of a silicone rubber or a silicone sponge rubber.
Description
FIELD OF THE INVENTION
The present invention relates to a pressure roller in a fixing
system of a xerographic copying machine, laser beam printer or the
like, in particular, it relates to a pressure roller used in a film
fixing system.
BACKGROUND OF THE INVENTION
As a pressure roller in a fixing system of a xerographic copying
machine, laser beam printer (hereinafter referred to as "LBP") or
the like, a roller has been proposed to improve toner release
properties which comprises a metal core, a rubber layer formed
around the metal core, and a fluororesin top layer provided over
the rubber layer.
Conventional rollers of this type are produced by a process
comprising steps of inserting a sleeve made of a fluororesin into a
cylindrical mold having a bore, which had an outer diameter smaller
than the inner diameter of the cylindrical mold; fixedly attaching
ends of the sleeve to the end plates of the mold by plugging the
bore cavity with the end plates for holding a metal core
concentrically with the bore; and filling the annular space thereby
formed between the bore and the metal core with a molten rubber
material under high pressure to expand the sleeve, thereby bringing
the rubber-filled sleeve into contact with the inner wall of the
cylindrical mold under pressure to unify the sleeve with the rubber
material (see, U.S. Pat. Nos. 3,613,168 and 3,724,983).
The elastic layer may be made of a silicone sponge rubber. To form
a top layer of a fluorocarbon polymer onto the surface of such a
sponge rubber layer, according to Japanese Laid-Open Publication
No. 6-266257, the silicone sponge rubber formed around the metal
core has its surface coated with an adhesive such as an
addition-reaction type silicone rubber, and the resultant is
inserted into a sleeve and heated to fix the sleeve thereto.
Such conventional pressure rollers produced by the above described
methods have problems. In particular, when such a pressure roller
is used in a film fixing system, slippage is likely to occur
between a film under image fixing and the pressure roller, thereby
causing image failure. In a film fixing system, a roller using a
silicone rubber having a high coefficient of dynamic friction as a
top layer, or a roller comprising a silicone rubber layer having
its surface coated with a mixture of a fluororubber with a
fluororesin such as Dai-El Latex GLS-213 (Daikin Industries Ltd.),
or the like is used as a pressure roller. However, these roller
have a drawback that life as a roller is short because of poor
toner releasing properties.
On the other hand, in a roller fixing system comprising a heating
roller and a pressure roller, hardness of an elastic layer of the
pressure roller is often designed to be very low in recent years.
Accordingly, a fluororesin layer as a surface layer of the pressure
roller and the elastic layer tends to be considerably different
from each other in stiffness. This may cause image failure also in
roller fixing system as in film fixing system.
SUMMARY OF THE INVENTION
The present invention has been made in view of these problems. It
is, therefore, an object of the present invention to provide a
pressure roller which is capable of forming a high quality image
free of image failure and which has excellent durability.
To attain the above objective, the pressure roller according to the
present invention comprises:
a metal core,
an elastic layer formed around said metal core, and
a top layer provided over said elastic layer, said top layer having
a thickness of not greater than 0.1 mm and being made of a
fluororesin, said fluororesin having a coefficient of dynamic
friction of 0.25 or more.
The elastic layer is preferably made of a silicone rubber or
silicone sponge rubber. Into the fluororesin, it is preferred to
incorporate at least one member selected from the group consisting
of a polyamide, polyester, thermoplastic fluororubber,
tetrafluoroethylene-hexafluoropropylene copolymer (ETFE),
tetrafluorethylene-hexafluoropropylene-vinylidene fluoride
terpolymer (THV).
The fluororesin is preferably made of a
tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA),
tetrafluoroethylene-hexafluoropropylene copolymer (FEP),
tetrafluoroethylene-perfluoromethyl vinyl ether (MFA) or
tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether
terpolymer (EPA).
According to the present invention constructed as described above,
a fluororesin sleeve made of a fluororesin having a coefficient of
dynamic friction of 0.25 or more, preferably 0.30 or more, more
preferably 0.40 or more is used as the top layer covering the
elastic layer formed around the metal core. By virtue of this, it
is possible to provide a pressure roller which causes no image
failure in film fixing and exhibits durability for a long period of
time.
In addition, the above effects of the freedom from image failure in
film fixing and the prolonged durability as a pressure roller are
further enhanced by the use of the silicone rubber or silicone
sponge rubber as the elastic layer, by the incorporation of at
least one member selected from the group consisting of a polyamide,
polyester, thermoplastic fluororubber,
tetrafluoroethylene-hexafluoropropylene copolymer (ETFE),
tetrafluorethylene-hexafluoropropylene-vinylidene fluoride
terpolymer (THV) into the fluororesin, and by the use of the
tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA),
tetrafluoroethylene-hexafluoropropylene copolymer (FEP),
tetrafluoroethylene-perfluoromethyl vinyl ether (MFA) or
tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether
terpolymer (EPA) as the fluororesin.
The pressure roller according to the present invention is
constructed as described above and thereby capable of exhibiting
the above functions. Therefore, the use of the pressure roller
having a coefficient of dynamic friction of 0.25 or more
successfully provides high quality images free from image failure
and extremely improved durability.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a cross-sectional view of an embodiment of the
pressure roller according to the present invention.
FIG. 2 is a schematic view illustrating a method for measuring a
coefficient of dynamic friction.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, embodiments of the present invention will be described with
reference to the accompanying drawings.
FIG. 1 shows an embodiment according to the present invention in
section, which is incorporated as a pressure roller used in a
fixing system of a copying machine.
The pressure roller 1 comprises a metal core 2, an elastic layer 3
made of a silicone rubber and formed around the metal core 2, and a
top layer 4 covering the elastic layer 3 and made of a fluororesin
having a high coefficient of dynamic friction.
To form the elastic layer 3, a silicone rubber composition is used
which comprises 100 parts by weight of XE20-B0068 (trade name,
manufactured by Toshiba Silicone Co., Ltd.) as a silicone rubber,
0.5 part by weight of TC-8 (trade name, manufactured by Toshiba
Silicone Co., Ltd.) as a vulcanizing agent, and 1 part by weight of
ME41-F (trade name of a red iron oxide silicone paste, manufactured
by Toshiba Silicone Co., Ltd.) as a pigment.
Properties of the silicone rubber as the elastic layer 3, which was
used in common for sample pressure rollers as Examples and
Comparative Examples (referred to as E and C in Tables given below,
respectively), in accordance with JIS K6301 are shown in Table 1.
Coefficients of dynamic friction of the fluororesin top layers of
the sample pressure rollers are shown in Tables 2 and 3.
TABLE 1 ______________________________________ hardness (JIS A) 10
tensile strength (MPa) 0.4 elongation (%) 410 tear strength (kN/m)
3 specific gravity 1.01 compression set (180.degree. C. .times. 22
hrs, %) 8 ______________________________________
TABLE 2
__________________________________________________________________________
Sample No. E1 E2 E3 E4 E5 E6 E7 E8 E9 E10
__________________________________________________________________________
composition FEP 95 80 70 80 of PFA 90 90 80 fluororesin EPA 90
(weight ratio) MFA 95 90 polyamide polyester 10 10 thermoplastic 5
20 10 20 5 10 ETFE 30 THV 20 coefficient of dynamic friction 0.30
0.40 0.30 0.30 0.25 0.25 0.30 0.25 0.25 0.30
__________________________________________________________________________
TABLE 3
__________________________________________________________________________
Sample No. E11 E12 E13 E14 C1 C2 C3 C4 C5 C6
__________________________________________________________________________
composition FEP 100 of PFA 100 95 fluororesin EPA 100 95 (weight
ratio) MFA 80 95 75 85 100 polyamide 5 5 5 polyester 25
thermoplastic 20 ETFE THV 15 coefficient of dynamic friction 0.40
0.30 0.30 0.30 0.20 0.15 0.15 0.20 0.20 0.20
__________________________________________________________________________
Particulars on the fluororesins in Tables 2 and 3 are as
follows.
FEP: Neoflon FEP NP-40 (Daikin Industries, Ltd.)
PFA: Neoflon PFA AP-230 (Daikin Industries, Ltd.)
EPA: Neoflon PFA SP-120 (Daikin Industries, Ltd.)
MFA: HYFLON MFA620 (Ausimont S.P.A., Italy)
polyamide: UBE Nylon 66 (Ube Industries, Ltd.)
polyester: Hytrel 4047 (Toray-Du Pont Co., Ltd.)
thermoplastic: Dai-El Thermoplastic T-530 (Daikin Industries,
Ltd.)
ETFE: Neoflon ETFE EP-540 (Daikin Industries, Ltd.)
THV: THV 500G (Sumitomo 3M, Ltd.)
With respect to each of the samples as Examples and Comparative
Examples, coefficient of dynamic friction was measured in
accordance with ASTM D1894 e. The method in accordance with ASTM
D1894 e will be described with reference to FIG. 2.
A sheet of paper for PPC 12 is placed on a paper sheet bed 11 which
is engaged with a threaded rod 10 rotationally driven by a motor
(not shown) and which is movable to-and-fro by the rotation of the
threaded rod 10. On the other hand, a sample roller 13 is cut from
a pressure roller. The sample 13 is first placed on the PPC paper
sheet 12 in such a manner that no substantial load is applied onto
the PPC paper sheet 12, and then normal load W.sub.0 is applied
thereon. Consequently, normal load W.sub.0 is exerted on the PPC
paper sheet 12. In FIG. 2, reference number 14 represents a
measuring rod fixedly attached to the sample 13, reference number
15 a distortion gauge on which the measuring rod 14 abuts,
reference number 16 an amplifier, and reference number 17 a
recorder.
The threaded rod 10 is rotated by the motor to move the bed 11
engaged therewith in the direction shown by arrow. In consequence
of the movement of the bed 11, the sample 13 placed on the PPC
paper sheet 12 placed on the bed 11 is moved together with the
measuring rod 14. By this movement, the tip of the measuring rod 14
abuts on the distortion gauge 15. On the other hand, the bed 11 is
further moved. As a result, the distortion gage 15 detects
frictional force F. The frictional force F is low with respect to a
sample having tendency to slide and high with respect to a
viscoelastic sample. Accordingly, a coefficient of dynamic friction
.mu. is derived from W.sub.0 and F and represented by the formula:
.mu.=F/W.sub.0, thereby enabling determination of the coefficient
of dynamic friction .mu..
Image printing test was conducted on the sample rollers provided
with a top layer made of a fluororesin having a coefficient of
dynamic friction of 0.25 or more, preferably 3.0 or more, more
preferably 4.0 or more (Examples 1 to 14) and the sample rollers
provided with a top layer made of a fluororesin having a
coefficient of dynamic friction lower than 0.25 (Comparative
Examples 1 to 6).
In the image printing test, 100 sheets of paper for PPC are
consecutively printed for each sample by means of Laser Writer 300
(manufactured by Apple Computer Japan Co., Ltd.) as an LBP. The
printed images are examined and evaluated in terms of number of
occurrence of image blur. The results of the image evaluation are
shown in Tables 4 and 5.
TABLE 4 ______________________________________ Sample No. E1 E2 E3
E4 E5 E6 E7 E8 E9 E10 ______________________________________ image
failure* 0 0 1 1 2 1 0 2 1 0 ______________________________________
*image failure: number of occurrence of image failure per
consecutively printed 100 papers
TABLE 5 ______________________________________ Sample No. E11 E12
E13 E14 C1 C2 C3 C4 C5 C6 ______________________________________
image failure* 0 0 1 0 6 20 20 7 12 10
______________________________________ *image failure: number of
occurrence of image failure per consecutively printed 100
papers
It is understood from Tables 4 and 5 that few image failures are
observed with respect to the pressure roller samples using a
fluororesin having a coefficient of 0.25 or more, no substantial
image failures are observed with respect to those using a
fluororesin having a coefficient of dynamic friction of 3.0 or
more, and no image failure is observed at all with respect to those
using a fluororesin having a coefficient of dynamic friction of 4.0
or more.
On the other hand, it is understood that image failures frequently
occur with respect to those using a fluororesin having a
coefficient of dynamic friction lower than 0.25.
Then, seventy thousand sheets of paper were consecutively printed
to evaluate durability of each of the samples. Each of the samples
showed no substantial change in frequency of occurrence of image
failure even after the consecutive printing of seventy thousand
sheets of paper and caused no substantial paper wrinkle or curl
which may adversely affects image forming. Accordingly, each of the
samples was found to have satisfactory durability.
Each of the pressure rollers used in the evaluation has an outer
diameter of 15.8 mm, a thickness of the silicone rubber elastic
layer of 3 mm, a thickness of the fluororesin top layer of 50 .mu.m
and a length of the elastic layer of 220 mm.
The fluororesin according to the present invention which has a
coefficient of dynamic friction as high as 0.25 or more is obtained
by mixing a highly viscoelastic secondary component with a known
fluororesin such as PFA, FEP, MFA or EPA.
There is no particular restriction with respect to the secondary
component, as long as it can be mixed with such a conventional
fluororesin and has a relatively high coefficient of dynamic
friction. For example, however, urethanes are not desirable because
of their poor heat resistance.
As examples of the secondary component used in the present
invention, there may be mentioned polyamide resins such as a nylon
6, nylon 66, nylon 8 (N-methoxymethyl nylon), nylon 11 and nylon
12; polyamide-based thermoplastic elastomers such as UBE-PAE (Ube
Industries, Ltd.), Pebacks (Elf Atochem Co., Ltd., France) and
NOVAMID PAE (Mitsubishi Chemicals Co., Ltd.); polyester resins such
as a polyethylene terephthalate and polybutylene terephthalate;
polyester elastomers such as Hytrel (Toray-Du Pont Co., Ltd.) and
Pelprene (Toyobo Co., Ltd.); thermoplastic fluororubbers such as
Dai-El Thermoplastic (Daikin Industries, Ltd.) and Cefral Soft
(Central Glass Co., Ltd.); a tetrafluoroethylene-ethylene copolymer
(hereinafter referred to as ETFE); and a
tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride
terpolymer (hereinafter referred to as THV).
In the present invention, there is no particular restriction with
respect to the type of the rubber used as the elastic layer 3. For
the pressure roller, however, a vinyl group-containing
organopolysiloxane composition, i.e., a silicone rubber is
generally used. A silicone sponge rubber is also used, if
desired.
As the silicone rubber, there may be used those vulcanizable with a
conventional peroxide vulcanizing agent such as
2,5-dimethyl-2,5-di(tert-butylperoxy)hexane. Examples of
commercially available silicone rubbers include DY32-420U,
DY32-421U, DY32-422U, DY32-576U, DY32-623U, DY32-910U and DY32-911U
(Dow.Corning Toray Silicone Co., Ltd.); KE520U, KE7019U and KE7020U
(Shin-Etsu Chemical Co., Ltd.); TSE221-3U and TSE270-4U (Toshiba
Silicone Co., Ltd.); and EL5251, EL5308 and EL5508 (Wacker
Chemicals East Asia Ltd.).
As the silicone sponge rubber, there may be used KE901U, KE903U or
KE904FU (Shin-Etsu Chemical Co., Ltd.); or XE21-A9915 (Toshiba
Silicone Co., Ltd.) in the presence of a foaming agent such as
azobisisobultyronitrile or 1,1-azobis(1-acetoxy-1-phenyl-ethane)
and a vulcanizing agent.
To the elastic layer 3, various additives such as a reinforcer,
filler, vulcanizing agent, coloring agent, conductive agent, heat
resisting material and pigment may be added according to
applications and design of the pressure roller.
There is no particular restriction with respect to the formulation
of additives incorporated into the elastic layer 3. For example,
however, approximately 10 to 300 parts by weight of a reinforcer
and a fille are generally added to 100 parts by weight of a base
rubber. As typical examples of the reinforcer, there may be
mentioned carbon black, hydrated amorphous silica or anhydrous
silica (fumed silica).
The hydrated amorphous silica is a reinforcer silica containing
silicon dioxide (SiO.sub.2), which may be produced by various
method. For example, it is prepared by directly decomposing sodium
silicate with sulfuric acid (direct method) or by reacting sodium
silicate with a salt to form a salt of silicic acid and then
decomposing the salt of silicic acid with sulfuric acid or carbon
dioxide (indirect method). As commercially available hydrated
amorphous silica, there may be mentioned Nipsil VN3 (Nippon Silica
Industries Co., Ltd.), Carplex CS-5 (Shionogi & Co., Ltd.),
Starsil S (Konoshima Chemical Co., Ltd.), Tokusil US (Tokuyama
Corporation), Silton R-2 (Mizusawa Industrial Chemicals Co., Ltd.),
Hisil 1223 (PPG Industries Inc., U.S.A.), Ultrasil VN3 (Degussa
Corp., Germany), or Vulkasil S (Bayer AG, Germany). It is noted
that those having a mean particle diameter of 30 .mu.m or less,
preferably 5 .mu.m are used.
The anhydrous silica is a reinforcer silica containing silicon
dioxide, which is produced by heat decomposition of a silicon
halide; heat reduction of quarts sand, followed by air oxidation of
vaporized SiO resulting therefrom; or thermal decomposition of an
organosilicic compound. As commercially available anhydrous silica,
there may be mentioned Aerosil 200 (Nippon Aerosil Co., Ltd.),
Aerosil R972 (Nippon Aerosil Co., Ltd.), Cab-O-Sil MS-5 (U.S.A.,
Cabot Corporation), or Reolosil QS102 (Tokuyama Corporation). In
the present invention, the hydrated amorphous silica and the
anhydrous silica may be used in combination, if desired.
Further, a wetter may be added with a view to preventing a
secondary bond due to surface activity of the silica. As the
wetter, there may be mentioned silicone resins, alkoxysilanes and
siloxanes, hydroxysilanes and siloxanes, silazanes, organic esters,
and polyhydric alcohols.
The fillers are an indispensable element of the elastic layer 3 for
maintaining mechanical properties of rubber, such as physical
strength, hardness, compression set, which are essential to the
functions of the elastic layer. As the fillers, there may be
mentioned calcium carbonate, ground quartz, diatomaceous earth,
zirconium silicate, clay (aluminum silicate), talc (hydrated
magnesium silicate), wollastonite (calcium metasilicate), titanium
oxide, zinc oxide, magnesium oxide, alumina (aluminum oxide),
chromium oxide, red iron oxide, aluminum sulfate, barium sulfate,
lithopone, molybdenum disulfide, mica, and graphite.
Various conductive agents may be used to impart electrical
conductivity to the elastic layer, thereby bringing volume
resistivity of the elastic layer to, for example, 10.sup.13
.OMEGA.*cm or less. The conductive agents include conductive carbon
blacks such as acetylene black and Ketjen Black (Ketjen Black
International Inc.); graphite; a powder of metal such as silver,
copper or nickel; conductive zinc oxide; conductive calcium
carbonate; and carbon fiber. Of these, carbon blacks are generally
used.
In the present invention, a heat resisting material such as cerium
oxide may be added. However, since the pressure roller of the
present invention is not of the type prepared by coating a silicone
rubber roller with a latex made of a mixture of a fluororubber with
a fluororesin, such as Dai-El LatexGLS-213 (Daikin Industries,
Ltd.), it is not necessary to subject the pressure roller to baking
at a temperature of approximately 300.degree. to 320.degree. C.
Accordingly, a heat resisting material such as cerium oxide may not
necessarily be added.
A pressure roller made of a silicone rubber is often colored in
red. In this case, a red iron oxide is generally used as a coloring
agent. As the red iron oxide, there may be used those for coloring
a rubber which are prescribed in SRIS (The Society of Rubber
Industry, Japan, Standard) 1108. When orientation of the coloring
agent is critical during processing, a spherical grade of red iron
oxide having a mean particle size of 0.3 .mu.m or less, such as
Byferrox 130M (Bayer AG, Germany) may be added to the silicone
rubber in an amount of approximately 0.2 to 2% by weight. Recently,
the coloring agent is added frequently in the form of a silicone
masterbatch in view of good dispersion and prevention of
scattering. For example, CP-21 (Dow. Corning Toray Silicone Co.,
Ltd.) containing approximately 50% of a coloring agent is added to
the silicone rubber in an amount of 0.3 to 4% by weight.
As the vulcanizing agent used in the present invention, when the
silicone rubber is of a heat curing type, organic peroxides for
vulcanizing a silicone rubber may usually be used. Such organic
peroxides include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide,
dicumyl peroxide, di-tert-butyl peroxide, tert-butyl perbenzoate,
p-monochlorobenzoyl peroxide, 2,5-dimethyl-2,5-di(tert-butyl
peroxy) hexane, tert-butyl cumyl peroxide, tert-butyl
peroxy-2-ethyl hexanoate, tert-butyl peroxyisopropyl carbonate,
1,1-bis(tert-butyl peroxy)-3,3,5-trimethyl cyclohexane, and
tert-butyl peroxy 3,5,5-trimethyl hexanoate. Of these, dicumyl
peroxide or 2,5-dimethyl-2, 5-di(tert-butyl peroxy)hexane is
generally used. It is, of course, possible in the present invention
to use heat curable organopolysiloxane compositions of an addition
reaction type comprising a vinyl group-containing organosiloxane,
an organohydrogenpolysiloxane and a platinum catalyst, instead of
the above-mentioned heat curing type compositions using organic
peroxides.
If desired, a conductive agent such as a conductive carbon black
may be added to the fluororesin used in the present invention to
obtain a conductive fluororesin having volume resistivity of
10.sup.13 .OMEGA..times.cm or less. A pressure roller may be formed
using the conductive fluororesin.
In the present invention, bonding between a sleeve for the top
layer 4 made of a fluororesin such as PFA, FEP, MFA or EPA and the
silicone rubber is effected by applying a silane-based adhesive
such as Chemlok 607 (U.S.A., Lord Corporation) to the inner surface
of the fluororesin sleeve which has been subjected to inner surface
activation, and bringing the elastic layer 3 made of a silicone
rubber into contact with the sleeve, followed by vulcanization of
the resultant.
As a method for the activation of the inner surface of the sleeve
made of a fluororesin such as PFA, FEP, MFA or EPA, there may be
mentioned a method comprising chemical treatment with a solution
prepared by dissolving metallic sodium and naphthalene in THF
(tetrahydrofuran) such as TETRA-ETCH (JUNKOSHA Corporation) or in
ethylene glycol dimethyl ether, a method comprising chemical
treatment with a solution prepared by dissolving metallic sodium in
liquid ammonia, a method comprising chemical treatment with an
amalgam of mercury with an alkali metal such as lithium, an
electrolytic reduction method, a corona discharge treatment method,
a method comprising treatment with a plasma of an inert gas such as
helium or argon, or a method comprising treatment with an eximer
laser.
The metal core 2 and the elastic layer 3 may be bonded together
using a silicone-based adhesive such as primer No. 16 (Shin-Etsu
Chemical Co., Ltd.). In this connection, the metal core 2 is
preliminarily surface-treated with a sand blast or the like and
degreased with methylene chloride or the like, and then an adhesive
is applied to the surface of the metal core, and if necessary,
baking is conducted at about 130.degree. C. for about 30
minutes.
The present invention has been described with reference to the
preferred embodiments. It is, however, to be understood that the
present invention is by no means restricted to the above
embodiments, and that many changes or modifications may be made
according to need.
* * * * *